1. Field of the Invention
The present invention relates generally to manufacture of ceramic powders for coating applications. Particularly, the present invention relates to the purification of metal oxide powder, such as yttria and alumina powders, for use in thermal spray applications.
2. Description of Related Art
High purity metal oxide materials are essential to scientific research and many high tech applications and manufacturing processes. These materials are used to make components or form surface coatings of similar purity. For example, other references have reported a yttrium oxide surface coating for semiconductor IC processing vacuum chambers and a multilayer coating system of high purity yttrium oxide and aluminum oxide for components inside a plasma treatment chamber. Others have disclosed a high purity aluminum oxide barrier layer for electrostatic chuck.
Thermal spray processes, especially plasma spray process, are widely used to form metal oxide coatings on various substrates. In order to deposit a high purity metal oxide coating, it is required that the feedstock material has to have a high purity and be able to be injected into the flame stably and consistently.
Complicated and expensive chemical processes are usually employed to manufacture high purity metal oxides. In order to manufacture materials suitable for thermal spray processes, several processes are currently used to modify the morphology of the material. Among them, plasma densification process can manufacture powders of spherical morphology and high density. Both of these characteristics improve the flowability of the powder. Good flowability of the feedstock helps to ensure the stability and reproducibility of the coating deposition process, and thus the consistency of coating quality.
Means for manufacturing highly purified yttria powder currently used in the art are costly and produce powder with comparatively poor flow characteristics. There remains a need in the art for a powder purification process that also improves flow characteristics and costs less than presently used methods.